I don't know about the game (I tried to play Halo 1 and 2 on PC. I did not enjoy the experience; and not having an XBawks sorta prohibited me from trying the other games in the series), but what I am a big fan of is the Soundtracks. Except for the Halo Wars one, they're all immensely listenable.
Neil Davidge's work here, while devoid of the iconic themes Marty McDonnell developed for the earlier games, is still really damn good. A track like "Arrival" delivers all the awesome you expect from a Halo OST, and if that's going to be the prototype for a new Halo theme, I would be happy indeed.